Diverse geophysical processes such as seismic and micro-seismic activity, volcanic activity, electric discharges from thunderstorms, vibrations introduced by human activities, and other phenomena generate propagating electromagnetic (EM) vibrations in the earth. The propagation and damping of these electric (E-type) and magnetic (B-type) emissions depend on the physical properties of the material in the earth. Differences in the local strength and phase characteristics of these electromagnetic vibrations can be used as indicators for the presence of water, hydrocarbons or minerals. These E-type and B-type oscillatory emissions always occur together. They can be measured separately by different sensing systems. My invention concerns an antenna system to measure E-type signals.
Moving survey platforms are used to collect such oscillatory electric signals using a three dimensional (3D) dipole antenna system. The survey platforms may consist of manned or unmanned aircraft, drones towed behind aircraft, drones suspended under helicopters, drones towed behind ships, ships, cars, trucks or a stationary object. Suitable electronic equipment is used to digitize and store these signals. The frequency of the signals of interest is in the order of 0.01 Hz to approximately 3,000 Hz. This invention concerns the antenna sensor system used to collect the oscillatory electric field strengths. A three dimensional antenna system consists of three independent dipole antenna systems that are mutually perpendicular as much as practical. The dipole antennas of a three dimensional system do not need to have a common point of intersection. The individual dipole antenna systems may be located anywhere on the survey platform. An individual dipole leg can range from approximately 0.1 meter to several meters, depending on practical limitations.
A description of prior art on which the currently used technology is based can be found in representative patents and patent applications. A patent describing similar technology is, for example: U.S. Pat. No. 7,002,350, U.S. that describes a three dimensional antenna system for a marine oil and gas exploration survey system.